Overnight, some 4000 metres deep on an “abyssal plain” in the mid-Atlantic Ocean, a black robotic hand plucked a bright orange cylinder from the wreckage field of Air France flight AF447 and stowed it inside a tiny remote-controlled submersible that delivered it to the cable-laying ship, which is being used to raise sections of the crashed airliner to the surface.

The cylinder is the memory module of the flight data recorder, which may provide answers to the many questions raised by the June 1, 2009, crash of the Airbus 332 jet with the loss of 228 people on board.

Why did that jet seem to fly straight through a line of towering tropical storms on a night when other flights crossing the same “inter tropical convergence zone”  diverted around storm cells capable of destroying any airliner ever designed?

Was it something unique to the A330 that caused it slam steeply at high speed with wings level and nose slightly elevated onto the surface of the ocean, or was it something to do with the conduct of the flight, meaning the flight safety culture of Air France? Or as is so often the case in air disasters,  a combination of factors that, on their own, might never had caused a crash?

These are very sensitive issues. They have been ferociously argued in European pilot forums,  and in the Euro media.  Since the crash the Air France pilots union has accused the company of wanting the world to forget their dead under the ocean and Air France has blasted the pilots in a memo for not focusing on their obligations to fly safely, an incredible outburst given the responsibility of the carrier for piloting standards.

Air France and Airbus are under formal investigation by the public prosecutor in Paris, which may lead to charges of involuntary manslaughter against individuals in both companies. The French accident investigator acknowledged at the outset that a known icing fault in the brand of external speed measuring devices (pitots) being used on that particular Air France jet was a factor yet “not the prime cause” of the accident.

It took that position at a press conference several weeks after the crash, and has not budged since, fuelling speculation that it knew more about the conduct of the flight at that early stage than it has so far chosen to reveal.

Since 1950, and excluding acts of terrorism, the Concorde disaster caused by runway debris, and the loss of a South American airliner flying a charter with an Air France flight number, the French flag carrier has tallied 1247 fatalities in 18 crashes, one of the bloodiest operational records in aviation.

The core of the flight data recorder retrieved overnight is intended to register over long periods of time a range of parameters covering the flight from pushback to disaster on its way from Rio de Janeiro to Paris.

If it is found to be readable, when it is opened in 8-10 days, it should show all of the key flight control inputs and positions, as well as the precise path flown, and the functionality of electrical and computer-based systems. These can then make better sense of incomplete automated status messages relayed in real time to the Air France operations centre in the minutes before a final message indicates rapid vertical acceleration by the jet.

The other flight recorder that the investigators are still searching for is the cockpit voice recorder,  which although it records over itself after some hours, should if recovered reveal how the relieving pilot and first officer conducted the flight and responded to the crisis that brought it down. (The captain had been due by then to have retired to a crew rest compartment before a return to the flight deck closer to France, and his body was among more than 50 sets of human remains found floating on the sea several days after the crash.)

The debris field of the jet contains more human remains, which the cable-laying ship intends to recover using cranes capable of lifting up to five tonnes to the surface.